DESCRIPTION: (Applicant's Description) One or both alleles of the FHIT gene are disrupted in a large fraction of many different types of human tumors. In tumor-derived cell lines and primary tumors with defined FHIT DNA alterations, there is a correlation between DNA alteration, detection of altered RT-PCR products and reduction in the level of Fhit protein. Additionally, replacement of Fhit expression in tumor cell lines suppresses tumorigenicity. This result has been confirmed by recent studies from another laboratory using an adenovirus/Fhit vector. Most recently, immunohistochemical studies of cervical, lung, gastric, bladder, pancreatic and kidney carcinomas have shown that large fractions of these primary tumors express reduced levels or no Fhit protein. This project will continue to study Fhit function by characterizing three possible Fhit, Nit or NitFhit interacting proteins identified from a D. melanogastor library using fly NitFhit as bait in yeast two-hybrid trapping experiments. The candidate interacting proteins are: 1) the c-terminus of the fly coracle protein, a homolog of mammalian 4.1 proteins; 2) a fatty acid binding protein homolog; 3) a fly polypeptide, Dcl5, without known homologs. The interactions will be confirmed in biochemical assays in fly or human systems. Each interaction pathway will then be dissected to understand its role in Fhit signaling. In parallel, Project 1 investigators will participate in characterization of deletions and arrangements of FHIT/FRA3B in specific cancer cells (with Project 2) and will prepare mutant Nit and Fhit proteins in the framework of structural predictions with Project 3.